Elements or Aperture?
They're very different programs. Aperture is an image management program with a good raw converter, while PSE is primarily a pixel editor with so-so image management and good raw conversion with fewer features.
For most people it's not an either/or question. Both have free trials (you can't get to the aperture trial in the app store, but it's available on apple's site), so download both and see which one suits your immediate needs the best.